STUDY DESIGN:

Retrospective Study OBJECTIVE.: The purpose of this study is to determine how BMI affects patient reported outcome measurements (PROMs) after lumbar fusions.

SUMMARY OF BACKGROUND DATA:

Although greater preoperative body mass index (BMI) is known to increase the rates of adverse events following surgery, there is a paucity of literature assessing the influence of BMI on PROMs after lumbar fusion.

METHODS:

Patients undergoing lumbar fusion surgery between 1-3 levels were retrospectively identified. PROMs analyzed were the Short Form-12 Physical Component Score (PCS-12), Mental Component Score (MCS-12), Oswestry Disability Index (ODI), and Visual Analog Scale (VAS) Back and Leg pain scores. Patients were divided into groups based on preoperative BMI: Class 1) BMI < 25.0; Class 2) BMI 25.0-29.9; Class 3) BMI 30.0-34.9; and Class 4) BMI ≥ 35.0. Absolute PROM scores, the recovery ratio, and the percent of patients achieving MCID between groups were compared.

RESULTS:

54 (14.8%) patients in Class 1, 140 (38.2%) in Class 2, 109 (29.8%) in Class 3, and 63 (17.2%) in Class 4 were included. All patients improved after surgery across all outcome measures (p < 0.001) except for Class 4 patients, who did not improve in terms of MCS-12 scores after surgery (p = 0.276). Preoperative PCS-12 (p = 0.002) and ODI (p < .0001) scores were significantly different between BMI groups-with Class 4 having worse disability than Class 1 and 2. BMI was not a significant predictor for any outcome domain. Overall 30- and 90-day readmission rates were similar between groups, with a higher revision rate in the Class 4 group (p = 0.036), due to a higher incidence of postoperative surgical site infections (p = 0.014).

CONCLUSION:

All patients undergoing short segment lumbar fusion for degenerative disease improved to a similar degree with respect to PROMs. However, those in the highest class of obesity (BMI ≥ 35.0) were at a greater risk for postoperative surgical site infection.

LEVEL OF EVIDENCE:

3.